Oscillator with amplifier coupling



April 16, 1940.

J. w. CONKLIN OSCILLATOR WITH AMPLIFIER COUPLING Filed April 30, 1937OSC/LLWTOH HMP.

12 Zmnentor James W Conlil in (Ittorneg LINE ' I1, the cathodes beingconnected to the grounded Patented Apr. 16, 1940 James W. Conklin,Audubon, N. J., assignor to Radio Corporation of- America, a corporationof Delaware Application April 30, 1937, Serial No. 139,839

3 Claims.

This invention relates to radio transmitting and receiving systems whichinvolve the use of a resonant concentric circuit for controlling theoperating frequency of an oscillation generator, and hasfor its,principal object the provision of an improved arrangement and method ofoperation whereby the generator frequency is rendered independent ofvariations or adjustments in the amplifiers to which the generator iscoupled. More particularly, the invention involves the use of a resonantconcentric circuit for the-dual purpose of stabilizing the generatorfrequency and coupling the generatorto the amplifier into which itfeeds. Prior to the present invention, it was customary to couple theconcentric circuit or line to the oscillator input circuit and toprovide the oscillator output with a tank circuit through which theoscillator was coupled to the amplifier. The present invention is basedon the discovery that utilization of the concentric line inthe'oscillator output as'a means of stabilizing the oscillator frequencyand coupling the oscillator to, the amplifier has the advantages of (1)improving the frequency stability for a given line, (2) permitting theoscillator controls to be fixed so that there are no operating controlshaving an im.- portant'efiect on frequency, (3) ermitting greaterflexibility in design due to the fact that the oscillator tube is notrequired to perform a dual function, and (4)- generally'improving theperformance of the system. v I

The invention will be better understood from the following descriptionwhen considered in connection with the accompanying drawing, and itsscopeis indicated by the appended claims. Referring to the drawing, aFigure 1 is 'a wiring diagram of the "conventional combined oscillatorand amplifier circuit heretofore utilized,

Figure 2, is a wiring diagram of the'improved oscillator-amplifiersystem as applied'to a generator of the negative transconductance type,and

Figures 3 and .4 are similar diagrams of modified embodiments of theinvention.

The well known system of Fig. 1 includes a cross-neutralized oscillatorH], which is provided with an input circuit including concentric conductors l l and i2 between which is interposed an input winding l3, andwith an output circuit including a tank circuit composed of aparallelconnected capacitor l4 and winding 15'. Suitable potentials are appliedto the oscillator input and output circuits,respectively, through leadsl6 and side of'the powersupply line. ln the oscillator devices. powerultra-high frequency oscillators of the resthe neutralizing condensersare used for regeneration control..

Coupled to the winding l5, through coupling capacitors l8 and I9, is across-neutralized tuned push-pull amplifier 20 which is provided 'withan I.

output winding 2!.

The primary function of the oscillator tank circuit formed by capacitorl4 and inductor I5 is toprovide a storage circuit of oscillatory powerat the operating frequency for supplying the load requirements, thedriving power for the succeeding amplifier in the present illustration.'A secondary function of the tank circuit isto provide a plate circuitimpedance incidental to the operaculating energy in the oscillator tankcircuit be large compared to the load supplied, in order that the loadvariations shall not greatly affect'the' 1 frequency and/or .theoscillation stability of-th e, oscillatorm It. is well known to the artthat in oscillator circuits employing frequency stabilizing or con.-

'trol means of the low power factor type, such as a piezo-electriccrystal or a concentric resonant line, it is desirable that thecirculating or stored energy be confined primarily to: the stabilizingIn -the prior art, particularly" in high onant line controlled type, ithas been necessary, for reasons explained the foregoing description', tohave considerable circulating energy in the oscillator tank circuit,represented by, ele- 1 r at) ments l4 and I5 of Fig. 1, which results'in an undesired division of the primary frequency determinationbetween line II and tank circuit l4 and I5. To confine the primaryoscillator frequency control to line I l, the tank circuit hi and I5Would preferably have low energy storage'and be of the broadlytuningtype. 1 I v As indicated above, this system leaves some thing to bedesired in that operationof the generator l 0 is not altogetherindependent of changes in the operating conditions or adjustments of theamplifier 20. Thepresent invention avoids this difliculty bytransferring the concentric line Il-I2 vtothe oscillator output circuit,where it functions both as the oscillator tankcircuit and as a couplingbetween theoscillator output and amplifier input circuits.

In the priorart practice, it has been considered of prime importance tominimizetheloadcoupled to the control line, in order to obtain a high Qcircuit with maximum. frequency stability, and the method of myinvention would have been considered improper, asit couples severaldevices, including the load'circuit, to the control line.

To prove the merit'of my invention, let E1 and E2 represent the totalcirculating energy present in the control line H--l2 and the oscillatortank circuit |4l5, respectively, referring to Fig. 1. Also let W1 and W2rep-resent the coupled load to these respective circuits, W1representing the oscillator grid losses and line losses, and W2representing the output load or amplifier. grid excitation power. Now itis a fact that the virtue of the line in controlling frequency is in onesense Now in the case of a high power ultra-high fre- "quencyoscillator, where the oscillator and ampliher will likely be similar, W2will probably'equal W1 and E2 will necessarily be of the same order asE1; therefore,

and

will be of the same order. Thus, we have two low power factor circuitsassociated with the oscillator, both capable of having a primary effecton cases of the same order of magnitude respectively.

Therefore, the power factor of the co'ntrol circuit will be of the sameorder as fier 23 and which may be provided with relatively adjustableplates 24 and 25 for adjustingitsca- 'pacity. The oscillator 22 is ofthe negativetransconductance type which is characterized bythe tuningtype.

factthat its output current varies inversely as the input voltages. Itincludes an inner grid 26 which functions as a suppressor grid, a secondgrid 27 which is subjected to a potential higher than that of the plateand functions as an anode,

and an outer grid 28 which functions as the control grid of theoscillator. .It will be noted that a resistor 29 is provided forreducing the plate voltage and limiting the plate current, that chokecoils 3i! and 3| are provided in the input and output circuits, that aresistor 32 is inter-U a capacitor 35 or altogether by theinterelectrode capacity of the oscillator tube which may be of theRCA-954 type.

Whensuch a pentode tube is used as a negative-transconductance tube, thegrid 26 isoperated at zero or slightly negative potential, the grid 21at high positive potential, the grid 28 at negative potential, andthe-plate at low positive potential. Under these conditions, the grids!functions as the primary anode, but, it being a mesh structure, part ofthe electrons pass through and are attracted to the slightly positiveplate. If the interposed grid 28 be given a suiiicientiy negative chargeto overcome the velocity of the electrons, they will return to thescreen grid, re-

Considering the grid 2? as the anode and the grid 28 sulting in anincreased screen current.

as the control electrode, the resulting transcon- Coupling between theinput. and output circuits may be effected in part by ductance isnegative, 1. e., within the range of operation, the anode currentdecreases when the control electrode is made more positive. Utilizedgrid 27 through the capacitor 35.

It will be observed that the negative-transconductance actionconsists'largely of an interchange of current between the plate and thegrid 21. This interchange is not complete, however, as part of thereturning electrons again made more negative. Further, while the controlgrid 26 plays no part in the normal action, it.

may be used to control the spacecurrentpwith a resulting great effect onthe negative resistance and amplitude of oscillations produced by thetube.

The oscillator output potential is applied to the concentric circuitHl2, which is tuned to the sions or by adjustment of the plates 2 i,25and which also functions to couple the oscillator output circuit to theinput circuit of the amplifier 23, with the advantages previouslydiscussed.

The system of Fig. 3 differs from thatofFig. 2 in that it includes across-neutralized oscillator 35 of the push-pull triode ,type,-providedwith an output winding 3% interposed in the oscillator grid circuits andlocated between the concentric conductors H and [2. The oscillator tankcircuit M--i5 is of the low-energy storage, broadly Coupling between theoscillator 35 and the'amplifier 2D is effected by means of an amplifierinput winding which is immersed in the field induced between theconductors II and l2 by the. current of the oscillator-output coil 36.The system of Fig. .4 differs from that of Fig. 3-

later is connected. between the concentric con in that the outputcircuit of asingle tube 05011,

.ductors II and I2 and coupling between the oscil- I lator input andoutput circuits is effected by means of a capacitor 39 and a. coillocated between the conductors II and I2.

It will, of course, be apparent that theinvenamplifier tuned to thefrequency of said oscillations, and means coupling said amplifierdirectly to said line so that the concentration of circulat ing energyin said stabilizer provides energyto drive said amplifier and to'controlthe frequency of said oscillations in the presence of changes in theload presented by said amplifier to said oscillator.

2. In a stabilized oscillator-amplifier, a concentric line resonator, athermionic discharge and reduces the effect of changes in tube, meanscoupling said discharge tube and said line so that sustainedoscillations are produced Whose frequency is maintained at apredetermined valuecorresponding to the resonant frequency of said line,a load device comprising a radio frequency amplifier tuned to thefrequency of said oscillations, means directly coupling said load deviceto said concentric line resonator so that the concentration ofcirculating currents in said resonator provides frequency stabilizationsaid load on said oscillations.

3. In a stabilized oscillator-amplifier, a thermionic tube having gridcathode and anode electrodes, a resonant line stabilizer, means couplingsaid stabilizer to said grid electrode, means ineluding said tube andstabilizer for generating ultra high frequency oscillations whosefrequency is determined by said stabilizer, an amplifier tuned to saidhigh frequency oscillations provided with input and output circuits, andmeans coupling said amplifier input circuits directly to said stabilizerfor impressing oscillations on said amplifier.

JAMES w. com.

